WAC 173-433-140

Criteria for impaired air quality burn bans.

Ecology or a local air authority may call an impaired air quality burn ban as follows:

(1) Stage 1 impaired air quality burn ban:

(a) Ecology or the local air authority may call a stage 1 impaired air quality burn ban when they predict that the twenty-four hour average of PM-2.5 levels will reach or exceed thirty-five micrograms per cubic meter within forty-eight hours.

(b) Pierce, Snohomish, and Yakima counties each contain at least one area at risk for nonattainment. In these counties, the local air authority may call a stage 1 impaired air quality burn ban when they predict that the twenty-four hour average of PM-2.5 levels will reach or exceed thirty micrograms per cubic meter within seventy-two hours.

(2) Stage 2 impaired air quality burn ban:

(a) Ecology or the local air authority may call a stage 2 impaired air quality burn ban when all of the following conditions exist:

(i) A stage 1 impaired air quality burn ban is already in effect and has not reduced the trend of rising PM-2.5 levels adequately.

(ii) The twenty-four hour average of PM-2.5 levels have already reached or exceeded twenty-five micrograms per cubic meter.

(iii) Ecology or the local air authority expects that PM-2.5 levels will remain above twenty-five micrograms per cubic meter for twenty-four hours or more from the time PM-2.5 levels reached the trigger in (a)(ii) of this subsection.

(b) Ecology or the local air authority may call a stage 2 impaired air quality burn ban without calling a stage 1 impaired air quality burn ban when all of the following conditions exist:

(i) The twenty-four hour average of PM-2.5 levels have reached or exceeded twenty-five micrograms per cubic meter.

(ii) PM-2.5 levels have risen rapidly.

(iii) Ecology or the local air authority predicts that the twenty-four hour average of PM-2.5 levels will exceed thirty-five micrograms per cubic meter within twenty-four hours.

(c) Pierce, Snohomish, and Yakima counties each contain at least one area at risk for nonattainment. In these counties, the local air authority may call a stage 2 impaired air quality burn ban without calling a stage 1 impaired air quality burn ban when all of the following conditions exist:

(i) The twenty-four hour average of PM-2.5 levels have reached or exceeded twenty-five micrograms per cubic meter.

(ii) PM-2.5 levels have risen rapidly.

(iii) The local air authority predicts that the twenty-four hour average of PM-2.5 levels will reach or exceed thirty micrograms per cubic meter within twenty-four hours.